For many biomass conversion processes, it is preferable to maximize diffusion and heat-transfer distances both across and along the grain. It is also preferable to cut across the fiber bundles rather than preserve their natural length. In addition, many biofuel processes require small feedstock particle sizes. Re-comminution of biomass feedstocks has introduced processing concerns. Milling and grinding affects biomass particle shape as well as size. For example, the hammer mill process tends to break wood chips multiple times along the grain, initially into narrow sticks (aka, pin chips) and eventually into narrower fiber bundles that tend to retain the full chip length. Likewise, grinding, wet milling, and crushing tend to separate biomass fibers without cutting across the grain. Such comminution machines often require dry biomass, at 15% wet basis (wb) or less, yet drying plant biomass below its fiber saturation point, approximately 40-45% wwb (˜30% dry basis), is an energy intensive process that may increase feedstock recalcitrance during conversion processing.
Thus, it would be advantageous to provide comminuted biomass particles with properties more favorable to biomass conversion processing.